Gaseous electric discharge arc lamp



NOV. 12, 1935. PlRANl ET AL 2,020,737

GASEOUS ELECTRIC DISCHARGE ARC LAMP Filed Dec. 14, 1953' JNVENTORS BY Hu y ATTO NEY Patented Nov. 12, 1935 UNITED STATES GASEOUS ELECTRIC DISCHARGE Marcello Plrani, Berlinewilmersdorf, and Alfred Riittenauer, Berlin-Halensee, Ge

rmany, II-

signors to General Electric Company, a corporation of New .York

Application December 14, 1933, Serial No. 702,426

Germany December 24, 1932 3 Claims. (01. l76-1) The present invention relates to gaseous electric discharge are lamps generally and more particularly the invention relates to such devices in which the arc voltage increases after the starting of the lamp and reaches its full'value after-the lamp has been operating an appreciable time. One type of lamp'having these voltage characteristics is known in the art as a high pressure metal vapor arc lamp.

Such lamps require a series resistance for the successful operation thereof and the series resistance can be in the form'of an incandescent filament mounted externally of the container of .the lamp. We have observed that in such a circuit the voltage acrossthe filament varies inversely with the arc voltage. Consequently, when the filament is designed to be heated to incandescence during the starting period of the arc discharge the filament is not heated sumciently during the operating period of the lamp when the arc voltage increases. On the other hand if the filament is designed to be heated to incandescence during the operating period of the lamp the filament is overloaded during the starting period when the arc voltage is low which causes said filament to burn out to terminate the useful life of the lamp unit.

The object of the present invention is to provide a lamp unit comprising a gaseous electric discharge are lamp having an incandescent filament connected in series therewith in which the filament is heated to incandescence and not overloaded during the starting and operation of the are lamp in the lamp unit. A further object of the invention is to provide an efiicient lamp unit of the above type. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description and from the appended claims.

In accordance with these objects the new and novel lamp unit comprises an arc lamp, a. series connected resistance in the form of a filament therefor, means to connect into and disconnect from the circuit a portion of said filament and an envelope enclosing these elements. All parts of the incandescent filament are connected into the circuit during the starting period when the are voltage is low and a part thereof is disconnected from the circuit during the operating period of the lamp when the arc voltage is high. The incandescent filament is thus at full brilliancy and is not overloaded during the starting and operation of the arc lamp. While many different types of time-delay switching means can be. used for switching a portion of theincandescent filament into and out of circuit we prefer a bi-metallic strip which bends in response to the heat generated by the arc lamp. "*While the incandescent filament and the control means therefor can be mounted in many positions with respect to the container of the arc lamp we prefer to mount these elements adjacent said container in order-to utilize the heat generated by the arc lamp to operate the switching means and (in order to utilize the heat from the filament to quickly raise to-and, maintain at its operating temperature the container'of the arc lamp. The are lamp and the incandescent filament thus form an efllcient lamp unit.

In the drawing accompanying and iormi part of this specification an embodiment of the invention is illustrated but as such illustrationis primarily for purposes of disclosure it will be understood, of course, that numerous changes in the form and details of the device and in its use and operation may be made by those skilled in the art without departure from the broad spirit and scope of the invention. In the drawing:

Fig. 1 is a front elevational view of the new and novel lamp unit,

Fig. 2 is a plan view of the incandescent filament and the switch mechanism therefor, and

Fig. 3 is a schematic view of the lamp circuit.

Like figures denote like parts in all views of mounted inside said envelope I. Said container 2 is supported by current leads 5 and 6 sealed into the pinch-part 3 of stem 4 of the envelope I and sealed into opposite ends of said container 2. A main discharge supporting electrode I of the arc lamp is connected by leads 6 and 9 with the screw-base I0 mounted on said envelope I. One end of a helically coiled, tungsten filament I2 is connected to said current lead 5 of the other maindischarge supporting electrode 8 by lead I I, the other end of said filament I2 is connected to the button-contact I 4 of the base I0 by lead I3. The screw-base I0 fits into the conventional screw-socket connected to the terminals of a or 220 volt current source. Said filament I2 is concentric with and is in a plane at right angles to the longitudinal axis of said container 2 mid-way between said electrodes I and 8. The external end of said lead 5 is connected to the lead I5 located in the stem 4 of the envelope I.

Said lead I5 has a resistance It connected there- 5 end of the container 2.

in and saidresistance It is mounted in said stem 4. Said lead I! is reintroduced in said envelope I and is sealed into said container 2, the end I! thereof terminating adjacent the electrode 1, as shown in Figs. 1 and 3. The end part I! serves as an auxiliary electrode to facilitate the starting of the main arc discharge between said electrodes I and I. Said electrodes 1 and l are electron emitting when heated and comprise a metal filament, such as a tungsten or nickel filament, coated or impregnated with an electron emitting material, such as barium oxide. It will be understood that we contemplate the use of other types of thermionic electrodes. Discs l1 and I8 of heat resisting material are connected to and are adjacent said electrodes 1 and 8 respectively and said discs l1 and I! are interposed between said electrodes I and 8. The filament l2 issupported in said envelope by rods I9, l9, I9, I9 and I9 fused into a glass knob 20 on the container 2,

as shown in Figs. 1. and 2. A bimetallic strip 2| is mounted on said lead 5 and is adjacent one A contact 22 for said bimetallic strip 2| is mounted on the support rod IQ of said filament |2.

Said container 2 has a gaseous atmosphere therein comprising a mixture of a gas and metal vapor, such as a mixture of argon and mercury vapor, or neon and sodium vapor, pool 23 indicating the source of the metal vapor. Said envelope 2 is filled with aninert gas, such as nitrogen or argon in accordance with the well known incandescent lamp practice.

When the above described lamp unit is connected to the terminals of a current source current flows through the lead II, the filament I2,

the lead IS, the resistance IS, the auxiliary electrode It, to the main electrode 1 and thence over the leads 6 and 9 to the basev Hi. The auxiliary discharge which takes place between said electrodes I5 and I ionizes the gaseous atmosphere in said container 2 and the main arc discharge starts between said main electrodes 1 and 8 as soon as .the gaseous atmosphere is sufliciently ionized. As soon as the main discharge is established in said container 2 the auxiliary discharge stops operating since the resistance in the discharge path between said electrodes 1 and 8 is less than the resistance of said resistance IS. The incandescent filament i2 is heated to incandecence on the starting of the auxiliary discharge which takes place when current is applied to the container 2 rapidly heats up said container 2 to its operating temperature. The vapor pressure of the metal in said container l rapidly increases to its operating pressure and the arc voltage likewise increases. The total length of the filament I2 is connected into the circuit during the starting period of the arc lamp when the filament voltage is high. The heat from said filament |2 and the heat from said container 2 heats the bimetallic strip 2| and said strip 2| bends more and more until contact is made between said strip 2| and the contact 22 which cuts out oicircuit the portion of said filament i2 located between said rod i9 and said lead H. This takes place at approximately the same time that the arc lamp reaches its operating voltage when the filament voltage is low. The other portion of the filament l2, that is, the portion thereof between said rod l9 and said lead I3 is thus at a high temperature during the operation of the arc lamp as well as during the starting of said lamp and consequently emits light of great intensity during 5 these periods to supplement the light emitted by the arc lamp. It will be understood of course that when the lamp unit is shut off the bimetallic strip returns to its contact breaking position when it has cooled sufiicientiy and the above described 10 operation takes place when current is again applied to the lamp unit.

The container 2 is heated during the operation of the device by the electric discharge therein and by the incandescent filament surrounding 15 said container 2 and the radiation of heat therefrom is reduced to a minimum by the gas-filled envelope I which is made of heat absorbing glass, when desired. The container 2 is thus at a high temperature during the operation 59 thereof which is of particular advantage in the type of lamp shown and described which is a high pressure mercury arc lamp in order to obtain a high metal vapor pressure. The high operating temperature of said container 2 is also 25 of advantage when the vapor of a diflicultly vaporizable material, such as an alkali metal, is used as a light giving element in order to obtain an efiective metal vapor pressure.

The new and novel lamp unit is useful as a generator of light radiations having therapeutic value, such as ultra-violet rays, in which case the envelope l and the container 2 are made of a material, such as quartz, which transmits such radiations.

What we claim as new and desire to secure by Letters Patent of the United States is:-

1. A lamp comprising an envelope, a gaseous electric discharge lamp device mounted in said envelope, an incandescent filament in said envelope, a part of said filament being connected in series with said lamp device during the starting and operation of said lamp device, another part of said filament being connected in series with said lamp device during the starting thereof and means to short-circuit said last named filament part during the operation of said lamp device.

2. A lamp comprising an envelope, a gaseous electric discharge lamp device mounted in said envelope, an incandescent filament in said en velope, a part of said filament being connected in series with said lamp device during the starting and operation of said lamp device, another part of said filament being connected in series 55 with said lamp device during the starting thereof and means responsive to temperature changes in said lamp device to short-circuit said last named filament part during the operation of said lamp device.

3. A lamp comprising an envelope, a gaseous electric discharge vapor lamp device mounted in said envelope, an incandescent filament in said envelope, said filament heating said lamp device during the starting and operation thereof, a part of said filament being connected in series with said lamp device during the starting and operation of said lamp device, another part of said filament being connected in series with said lamp device during the starting thereof and means to short-circuit said last named filament part during the operation of said lamp device.

. MARCELLO PIRANI.

ALFRED Rii'rrENAUER. 

